Cellular telephony is one of the fastest growing communication services. It is also one of the most rapidly evolving areas in terms of technology, services, standards, and service providers. At this time, many options are being considered for the next generation (generally called "third generation") of wireless communication systems, including extensions and additions to existing cellular systems, wireless ATM, and wireless Internet. It is a challenge to build wireless network infrastructure (particularly a switching system) that can meet the needs of yet to be built systems in a cost- and performance-effective way because of the uncertainty as to which technologies will be widely accepted and because it is likely that several sets of standards and technologies will co-exist. For a good description of third generation cellular systems, see IEEE Personal Communications Magazine, Special Issue on IMT2000: Standards Efforts of the ITU, Vol. 4, No. 4, August, 1997.
Third generation systems will require increased capacity because the number of users and bandwidth required for advanced services will greatly increase. For this reason, these systems will use digital air interfaces, and will use smaller cell sizes to increase frequency re-use. The increase in number of network access points (cell sites) requires that more equipment be deployed to concentrate onto a backbone network. This equipment must be inexpensive to allow networks with large coverage areas to be built. To be cost effective, systems should be scalable so that a range of installations, from small and inexpensive to large and high capacity, can be supported.
Third generation networks will also provide an expansive set of services, including telephone services available on modern ISDNs, location-based services, data services, and multimedia communication. Signaling protocols and control procedures must be added to existing systems to support these new services while interworking with existing services. An ideal system will allow new services to be added to existing systems without requiring major software modifications.
Because it is unlikely that there will be a single protocol suite or network type for third generation systems, these systems will have to interwork. In addition, third generation systems will be required to interwork with second generation systems. An ideal system will define a set of functions that cannot only interwork with different networks, but be used to implement different systems without major software redevelopment.
Summarizing, the next generation of wireless infrastructure requires a switching arrangement that is scalable to support inexpensive small installations, and flexible to support the easy introduction of new services and interwork with emerging systems without major software modifications.
One approach to a third generation cellular wireless telecommunications switching system that has been tried in the past is called Wireless Distributed Call Processing Architecture (W-DCPA). This approach is described in a first article authored by La Porta, T. F. Veeraraghavan, M., P. Treventi, R. Ramjee, entitled "Distributed Call Processing for Personal Communications Services," published in IEEE Communications Magazine, Vol. 33, No. 6, June, 1995, and in a second article authored by T. F. La Porta, M. Veeraraghavan, R. W. Buskens, entitled "Comparison of Signaling Loads for PCS Systems," published in IEEE/ACM Transactions on Networking, Vol. 4, No. 6, December 1996.
The W-DCPA approach has several drawbacks. First, it does not allow for graceful evolution from existing systems to a third generation approach, but rather requires a "flash cut" from existing to new equipment. Second, components internal to W-DCPA had various interfaces to other entities in the telecommunications network, which were non-standard. Therefore, W-DCPA was not arranged or able to use existing call processing and mobility management application layer protocols.